For quite some time, irregularly shaped parts have been coated by centrifugal techniques known as dip/spin or Filwhirl processing. In these batch processes, parts are loaded into a basket made of metal screen or perforated metal. In the dip/spin process, the basket of parts is dipped into a tank or vat of coating liquid. After immersion, the basket is raised, allowed to drain momentarily and then spun at speeds of typically 80 to 550 RPM. During spinning, excess coating is thrown from the parts until only a uniform thin film remains. The surplus coating is collected and returned to the coating bath. The Filwhirl process is identical to dip/spinning except that the coating is pumped into the basket until all the parts are flooded. Then the liquid is drained and the basket of parts is spun at 900 to 1,200 RPM.
A wide variety of parts, including coiled springs, screws, fasteners and much more are coated by the centrifugal methods described above. The technique eliminates time consuming handling of individual parts and ensures optimum utilization of coating.
However, until the present invention it has not been possible to uniformly coat nuts, or other parts with similar symmetries such as bushings, bearing sleeves, electrical meter yokes, etc. by the dip/spin or Filwhirl processes. In these batch processes parts are randomly oriented in the basket. However, unless the hole in a nut or other center-bored part is oriented parallel to the line of action of the centrifugal force generated during spinning, excess coating will accumulate along one wall of the internal diameter and the coating thickness in the center hole will exceed allowable tolerances.
It is therefore an object of the present invention to provide a means for separating and orienting parts during the spin cycle of the dipspin or Filwhirl coating method so as to result in improved coated parts.
It is a further object to provide a means for automatically separating and orienting certain center-bored parts, especially certain nuts and threaded female fasteners, during the spin cycle of a dip/spin or Filwhirl process in order to obtain a uniform coating on internal surfaces.
In general, the present invention relates to orientation means for centrifugals. More particularly the invention relates to an insert for the work basket or container of centrifugals which will orient parts therein. The objectives of the present invention can be achieved by providing in combination with the container or work basket of a centrifugal, means for orienting the parts within the container comprising an inner member fixed for rotation with the container for initially receiving the parts and at least one apertured or screen member circling the inner member and forming at least one compartment around the inner member between the side wall of the container and the inner member. The inner member which is fixed for rotation with the container is spaced from the top of the container so as to permit parts to pass and is sloped so as to permit centrifugal force to carry the parts therein out of the inner member as a result of centrifugal force during a spinning cycle. The apertured member is spaced from the top of the container and forms a compartment with the wall of the container which has a size so as to receive and orient a part therein in a direction in accordance with the shape or size of the part.
More specifically, the invention described herein provides a means to automatically separate and orient certain center-bored parts during the spin cycle of a dip/spin or Filwhirl coating machine in order to obtain a uniform coating on internal surfaces. Ordered orientation of the parts is accomplished by means of a hollow cone-like member that is inserted into the centrifugal basket or container. Typically, the basket is a canister made of metal screening or heavy mesh surrounded by a reinforced frame. The conical insert may be non-apertured but is preferably made of metal screening, [or] mesh or perforated metal and its maximum diameter is slightly smaller than that of the basket's wall. The smaller end of this cone-like member is preferably attached to the center of the floor of the centrifuge basket. Around the perimeter of this cone, from the floor of the basket straight up to the top edge of the cone, may be attached or integral therewith, a metal support of screening or heavy mesh forming the outer member. The distance between this supporting wall and the inner wall of the basket is preferably chosen to be greater than the thickness of the part to be coated, yet also less than the smallest diameter of said part. The orienting means of invention most preferably consists of an inverted cone enclosed in a cylinder such that the cross-section of the device has the shape like the letter "M".
The distance between the outermost cylindrical wall of the orienting device and the basket wall is preferably set to be greater than the thickness of the part to be coated, but also less than the smallest diameter of said part. This spacing is advantageous to the function of the invention because, during operation, properly oriented parts become trapped in the compartment or slot.
Parts are loaded directly into the cone portion of the insert. As the basket accelerates during the spin cycle, the parts move up the cone's wall as they are forced toward the outer walls by centrifugal forces. When the parts reach the top of the cone, those that are oriented with center holes parallel to the line of the centrifugal force will fall into the compartment or slot formed by the supporting wall or outer member of the insert and the wall of the basket. When the basket stops, that portion of the load that was not properly aligned, falls back down into the cone, but properly oriented parts remain trapped in the compartment or slot. Starting and stopping the basket again forces more parts into the slot, and eventually (usually after only several pulses) the entire load can be preferentially oriented in this manner.